Plants` `nervous system` discovered

London: Plants "remember" and "react" to information encrypted in light as well as transmit information about light intensity and quality from leaf to leaf, a process that is strikingly similar to the human nervous system.
These "electro-chemical signals" are carried by cells, which act as plant "nerves".

Led by Professor Stanislaw Karpinski, from the Warsaw University of Life Sciences in Poland, researchers used fluorescence imaging to observe the plants`` response.

The research team found that light shone on to one leaf generated a response from the whole plant.

The response, which took the form of light-induced chemical reactions in the leaves, continued in the dark.

This demonstrated, said scientists, that the plant "remembered" the information encoded in light.

"We shone the light only on the bottom of the plant and we observed changes in the upper part," The BBC quoted Prof Karpinski, as saying.

"And the changes proceeded when the light was off... This was a complete surprise," he added.

Prof Karpinski and his team found that when light triggered a chemical reaction in one leaf cell, it kicked off a "cascade" of events and that this was immediately signalled to the rest of the plant via a specific type of cell called "bundle sheath cell".

The researchers were even more intrigued when the plants`` responses changed depending on the colour of the light that was being shone on them.

Prof Karpinski felt plants might use the information encoded in the light to stimulate protective chemical reactions. He and his team analysed this more closely by investigating the effect of different colours of light on the plants`` immunity to disease.

Prof Karpinski said: "When we shone the light for on the plant for one hour and then infected it [with a virus or with bacteria] 24 hours after that light exposure, it resisted the infection."

"But when we infected the plant before shining the light, it could not build up resistance.

"[So the plant] has a specific memory for the light which builds its immunity against pathogens, and it can adjust to varying light conditions."

He also said plants used information contained in the light to immunise themselves against seasonal pathogens.

Prof Karpinski explained: "Every day or week of the season has... a characteristic light quality.

"So the plants perform a sort of biological light computation, using information contained in the light to immunise themselves against diseases that are prevalent during that season."